This relates generally to imaging systems, and more particularly to imaging systems for detection of chemical molecules.
Modern electronic devices such as cellular telephones, cameras, and computers often use digital image sensors. Imagers (i.e., image sensors) may be formed from a two-dimensional array of image sensing pixels. Each pixel receives incident photons (light) and converts the photons into electrical signals. Image sensors are sometimes designed to provide images to electronic devices using a Joint Photographic Experts Group (JPEG) format.
Imager sensors are sometimes used in microfluidic devices to image molecules. A molecule that is to be imaged may sometimes be referred to herein as an analyte or an analyte molecule. In such scenarios, an image sensor has an active surface that is covered with a layer of a chemical anchoring agent which bonds with molecules such as deoxyribonucleic acid (DNA). A fluorescent emitter is selectively attached to the molecules and light emitted by the fluorescent molecules is captured and converted into image data by the image sensors. However, the molecules bond randomly over the chemical anchoring agent layer and therefore there is the potential for cross-talk between image pixels. For example, a DNA strand may bond to the active surface of the image sensor in a region between multiple pixels such that light emitted by a fluorescent molecule coupled to the DNA strand is absorbed by each of the pixels.
To help reduce the effects of cross-talk, the active surface of the image sensor is sometimes etched to form wells prior to depositing the chemical anchoring agent layer. Subsequently, a mechanical polishing step is performed to remove the chemical anchoring agent in regions outside of the wells of the active surface. However, mechanical polishing to remove chemical anchoring agents can be unreliable and subject to substantial manufacturing variations. It would therefore be desirable to provide imagers with improved spatial resolution.